When someone takes a sexual innuendo so far as to make in uncomfortable for the others participating in the good times, and ultimately embarrassing themselves due to lack of social grace. The b-line is also crossed when recounting situations and to much detail is given on some of the more personal parts of the story.

"Brad crosses the b-line when he talks about fire crotches"
"You crossed the b-line with that one."

When someone takes a sexual innuendo so far as to make in uncomfortable for the others participating in the good times, and ultimately embarrassing themselves due to lack of social grace. The b-line is also crossed when recounting situations and to much detail is given on some of the more personal parts of the story.

"Brad crosses the b-line when he talks about fire crotches"
"You crossed the b-line with that one."